Git. No Auto Merge.

Mark Tinsley

We're moving to Git from PVCS. One thing we can't quite figure out: auto-merging. It seems this can get you into trouble. For instance, if we start with:

public function getStuff()
{
    $var1   = 'cool cats';
    $result = null;

    foreach ($this->allStuff as $curStuff)
    {
        if ($curStuff == $var1)
        {
            $result = 'indigo';
            break;
        }
    }

    if ($result === null)
    {
        $result = $this->allStuff;
    }

    return $result;
}

Then coder 1 changes it this way in their branch:

public function getStuff()
{
    $var1   = 'cool cats';
    $result = null;

    foreach ($this->allStuff as $curStuff)
    {
        if ($curStuff == $var1)
        {
            $result = 'indigo';
            break;
        }
    }

    if ($result === null)
    {
        $result = 'chicken nuggets';
    }

    return $result;
}

And, coder 2 changes it this way:

public function getStuff()
{
    $var1   = 'cool cats';
    $result = 'berries';

    foreach ($this->allStuff as $curStuff)
    {
        if ($curStuff == $var1)
        {
            $result = 'indigo';
            break;
        }
    }

    return $result;
}

The result would be this (making coder 1's changes bascially dead code):

public function getStuff()
{
    $var1   = 'cool cats';
    $result = 'berries';

    foreach ($this->allStuff as $curStuff)
    {
        if ($curStuff == $var1)
        {
            $result = 'indigo';
            break;
        }
    }

    if ($result === null)
    {
        $result = 'chicken nuggets';
    }

    return $result;
}

Of course, this is a simplified explanation in order to help explain my question. Has anyone had any trouble with this? Does anyone see this as an issue?

Balázs Szakmáry

As far as I can see, what you want in the end is exactly the result, minus the last if ($result === null) block.

If you do (you should ) have any static analysis of your codebase, it will mark this as dead code and eventually someone will remove it.

From the point of view of the correct functionality of the compiled code this is not really an issue. Also, in practice, anything even slightly more complicated than this will not be auto-merged and then the person doing the merge can solve the conflict in a more intelligent way.